He apparently took the sheet from his bed to his bathroom supposedly to wash it after being served breakfast.

Instead he used it take his own life by attaching it to the concrete and metal bars that covered the window. He is also believed to have used a stool.

"The deceased was found hanging in the shower of his detention cell, with a sheet around his neck tied to the window of the bathroom," read the protocol of the Rishon LeZion magistrate's court hearing on a request to loosen a gag order on the case.

Zygier, who was born in Australia but had joint nationality after emigrating to Israel, was found dead in his maximum security cell in Ayalon Prison in Ramla, near Tel Aviv, in December 2010 despite being supposedly subject to round-the-clock surveillance from in-cell cameras.

Guards had been instructed to check on Zygier, who they only knew as Prisoner X, at 20 or 25 minute intervals rather than every few minutes because he was not believed to have suicidal tendencies, the newspaper Maariv reported a preliminary inquiry conducted by the Israeli Prison Service as concluding.

That provided enough time for Zygier to kill himself without guards rushing in to stop him.

Prison service officials said it would be impossible to stop an inmate attempting suicide unless they had been deemed at risk by mental health professionals. In that case, they would be accommodated in a specially padded cell without implements or possibly restrained to a bed 24-hours-a-day.

The former Australian foreign minister, Alexander Downer, has dismissed suggestions that Zygier's Israeli spymasters incarcerated him in February 2010 because he had passed Mossad secrets to Australia's domestic intelligence agency.

The Australian Broadcasting Corporation reported on Monday that Zygier had told ASIO agents about sensitive Mossad operations, including one to set up a shell company in Italy that would export electronic equipment to Iran and Arab countries.